Acoustical deformability of giant unilamellar vesicles

An acoustic standing wave is used to trap and deform giant unilamellar vesicles with a diameter ranging from 10 to 50 μm. The giant unilamellar vesicles are prepared in glucose solution with a bi-layer of DOPC membrane with approximately 10 nm-thickness. They are suspended in a 4 cm2-chamber of an acoustofluidic device. The density of the vesicles is about 98% of the external solution density. The device operates with a single-frequency at 6 MHz producing a standing wave of 250 μm-wavelength, which is much larger than the vesiclesu0027 radii. To explain the observed deformability, we propose an acoustic deformation model as follows. The radiation stress, caused by the interaction of the standing wave and a vesicle, is obtained in the long-wavelength limit. Using the deformation theory of thin spherical shells, we show that the aspect ratio of a deformed vesicle is 1 + 2δ, where δ is inversely proportional to Youngu0027s modulus and directly proportional to the density contrast between the vesicle and the solution...